1. Field of the Invention
The present invention relates to novel compounds useful as host materials in making electronic devices. The invention further relates to electronic devices having at least one active layer comprising such a host material.
2. Background
In organic photoactive electronic devices, such as organic light emitting diodes (“OLED”), that make up OLED displays, the organic active layer is sandwiched between two electrical contact layers in an OLED display. In an OLED the organic photoactive layer emits light through the light-transmitting electrical contact layer upon application of a voltage across the electrical contact layers.
It is well known to use organic electroluminescent compounds as the active component in light-emitting diodes. Simple organic molecules, conjugated polymers, and organometallic complexes have been used.
Devices that use photoactive materials frequently include one or more charge transport layers, which are positioned between a photoactive (e.g., light-emitting) layer and a contact layer (hole-injecting contact layer). A device can contain two or more contact layers. A hole transport layer can be positioned between the photoactive layer and the hole-injecting contact layer. The hole-injecting contact layer may also be called the anode. An electron transport layer can be positioned between the photoactive layer and the electron-injecting contact layer. The electron-injecting contact layer may also be called the cathode.
Certain properties of materials used in films in electronic devices rely on a relatively high Tg in addition to the ability to form films.
CBP and mCP are commonly used as host materials in OLEDs; however they have limitations. CBP has a modest Tg and has a low lying triplet energy, making it a poor host for deep blue phosphorescent emissive systems. mCP has a higher triplet energy, making it more suitable for blue emissive systems, but has an undesirably low Tg.
There is a continuing need for host materials for use in electronic devices.